Sign of Aggression ?

My male cat Cosmo (4 years old) just recently started to bight the male kitten (5 months old) on the back of his neck. He isn't bighting hard enough to do any damage. (Kitty doesn't cry or try to run)

Is this normal behavior?

Hmm... I hope I can express this in a way that will convey my message!

When I brought my second cat home, my first cat... was in shock, she was just... so aggressive.. agitated.. rigid.. wouldn't move. paranoid... this was not the cat I had come to know... a week passed... two weeks pass..

One day, I come home to find them sleeping next to each other... and now they always sleep next to each other.. groom each other.. just best of friends but!

They play-fight all the time.. the thing is... and this is where I might have trouble conveying my message....

They bite each other, they scratch each other , they wrestle... but the bites don't actually hit anything lol... like they mimic the action of biting but they stop before they actually touch anything... they paw each other, but don't really scratch... they wrestle and then they groom and then they wrestle lol. They bite each other and then sleep next to each other, then they bite some more..

So really, to me its play-fighting and all innocent.. they just love having fun wih each other, play games.. play "hide and go seek" lol and chase toys together... fight over treats.... and not once have they actually caused trauma to each other.

So , if you can actually see it all being fun and games and nothing serious is happening and after the little physical interaction they are chilling and all is good.. then I dont think its a problem.

He's showing him who's boss :-)!

^ I agree with that. Your kitten is growing bigger and your older cat is making sure the youngster still knows who is in charge. It's normal for cats to establish dominance and give reminders. As long as there is no blood shed you just have to let them work it out amongst themselves.